解释下列词语
①震惊
②郑重
①令人震动而惊异。②严肃认真。
某生物正常体细胞中含有a条染色体,该细胞在分裂过程中,染色体的数目变化情况是( )。
23 ×15=
0.324÷0.01=
4÷ 49 =
109 ×1 45 =
0× 23 ÷3=
3.2x﹣1.9x=
2a+1.5a=
24×4%=
1.25×25×8×0.4=
( 23 ﹣ 19 )×18=
— What a heavy rain! Will it last long?— . We're getting into the rainy season now.